An interesting note. I was 9 when Ali fought Frazier in 1970 in what was the best fight of the 20th century. A fight, ironically, Frazier won. Frazier nearly took off Ali's head in the 15th round with a devastating left hook and Fraziers left hook was the best I've ever seen bar none. Ali amazed everyone by getting back up after a shot that would have killed a normal man.
What most people don't know is that Frazier went so far over the line in human endurance in defeating Ali that he almost died from kidney Failure and was never the same fighter again.
That was also the case after The Thrilla in Manila. Both fighters went so far over the line that fight that they were shadows of their former selves.
After Ali's first fight with Norton, he had this to say:
“Ken Norton is the best man I’ve ever fought," Ali said. "He is better than Joe Frazier, Jerry Quarry, Sonny Liston—any of them.”
Norton was considered to have no chance against Ali and Norton ended up breaking Ali's jaw and Ali ended up fighting the next 10 rounds with the jagged edges poking into his mouth.
Ali's corner man, said that at the end of each round he had to shake the mouth piece to get all the blood out of it and into the bucket.
For the second Ali / Norton fight Ali trained for over 14 weeks, more then he ever trained for anyone else, at that time.
Looking at Norton; he looked powerful enough to actually kill another fighter, if he really connected.
Even though Ali won the next two fights, he always had respect for Norton.
Norton died in September of 2013, at the age of 70.
I would love to see them greeting each other, in the afterlife.